[PATCH] ipa/103989 - avoid IPA inlining of small functions with -Og

[Richard Biener]

The following change avoids doing IPA inlining of small functions
into functions compiled with -Og - those functions will see almost no
followup scalar cleanups so that the benefit anticipated by the
inliner will not be realized and instead the late diagnostic code
will be confused by dead code that is left around.

Bootstrap & regtest pending on x86_64-unknown-linux-gnu.

OK?

Thanks,
Richard.

2022-01-18  Richard Biener  <rguenther@suse.de>

	PR ipa/103989
	* ipa-inline.cc (inline_small_functions): Do not enqueue call
	edges originating in functions compiled with -Og.

	* g++.dg/opt/pr103989.C: New testcase.
---
 gcc/ipa-inline.cc                   |  7 ++++++-
 gcc/testsuite/g++.dg/opt/pr103989.C | 30 +++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/opt/pr103989.C

diff --git a/gcc/ipa-inline.cc b/gcc/ipa-inline.cc
index 38522771118..f8bb072c422 100644
--- a/gcc/ipa-inline.cc
+++ b/gcc/ipa-inline.cc
@@ -2029,7 +2029,12 @@ inline_small_functions (void)
       struct cgraph_edge *next = NULL;
       bool has_speculative = false;
 
-      if (!opt_for_fn (node->decl, optimize))
+      if (!opt_for_fn (node->decl, optimize)
+	  /* With -Og we do not want to perform IPA inlining of small
+	     functions since there are no scalar cleanups after it
+	     that would realize the anticipated win.  All abstraction
+	     is removed during early inlining.  */
+	  || opt_for_fn (node->decl, optimize_debug))
 	continue;
 
       if (dump_file)
diff --git a/gcc/testsuite/g++.dg/opt/pr103989.C b/gcc/testsuite/g++.dg/opt/pr103989.C
new file mode 100644
index 00000000000..4604811b42a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr103989.C
@@ -0,0 +1,30 @@
+// { dg-require-effective-target c++17 }
+// { dg-options "-Og -Wall" }
+
+#include <optional>
+#include <memory>
+
+struct A {
+  A (int a) : a {a} 
+  {}
+
+  const std::shared_ptr <int> x;
+  int a;
+};
+
+class B
+{
+public:
+  B (const std::optional <A>& a)
+    : a {a}
+  {
+  }
+public:
+  const std::optional <A> a;
+};
+
+int
+main ()
+{
+  B b {std::nullopt};
+}
-- 
2.31.1